1. Field of the Invention
The present invention relates to a technique for controlling an exposure apparatus.
2. Description of the Related Art
A semiconductor exposure apparatus uses an XY stage for moving a wafer to a desired position. Data that shows how the XY stage is moved along time is called a “target locus”. The target locus of the stage during the period from when an exposure ends to when the next exposure starts needs to satisfy the following three conditions:
(1) a start condition of velocity and position at the end of an exposure;
(2) an end condition of position and velocity at the start of the next exposure; and
(3) a constraint condition that the acceleration and velocity for driving the stage should not exceed an upper limit value.
Furthermore, the target locus is required to reduce driving time as low as possible so as to improve productivity. With conventional techniques, for example, Japanese Patent Laid-Open No. 2010-087470 discloses that the start condition and the end condition are satisfied by matching the timing of driving in the X direction with the timing of driving in the Y direction. Japanese Patent Laid-Open No. 2010-147467 discloses that the driving time is shortened by improving the scan velocity during exposure. Furthermore, Japanese Patent Laid-Open No. 2005-183966 discloses that the driving time is shortened by reducing the settling time for improving overlay accuracy.
According to the documents mentioned above, when creating the target locus between exposures, the target locus is created by giving higher priority on satisfying the start condition and the end condition and bringing the velocity and acceleration within the constraint condition. For this reason, none of the documents necessarily guarantees minimization of driving time. Accordingly, it can be said that there is room for improvement in throughput.